1. Field of the Invention
The present invention relates to an automatic emergency stop apparatus for preventing counter flow and counter fire of gaseous bodies in gas conveying pipes.
2. Description of the Prior Art
When counter flows and counter fires are caused in gas installation piping, obstacles and explosion hazards are caused throughout the installation piping. Two methods have been considered for preventing these disadvantages. One has been the removal of the causes for the production of counter flows and counter fires and the other has been the mitigation of counter pressures caused by impact waves and preventing the diffusion of counter flames when the counter flows and the counter fires have been caused.
Counter flows can be prevented through the utilization of conventionally known check valves in the gas flow passage. However, substantial accessory structures are required to prevent counter fires from being caused. In addition, pressure, temperature, etc. of the gas has to be taken into consideration. It is extremely difficult, in terms of technique, to prevent counter fires from being caused; and as a result it is still impossible to completely prevent counter fires. Accordingly, at the present time, research and development is performed only on the mitigation of impact waves and the prevention of counter-fire diffusion. The present invention is developed along this policy.
One technique for counter-pressure mitigation and counter fire diffusion prevention in conventional gas appliances is disclosed in Japanese Patent Publication No. 7983/1958. According to this patent, a by-pass is formed in the gas flow passage so that the gas flows through the by-pass during normal gas flow. During the production of counter fires, a check valve installed in the flow passage is depressed by the counter pressure to close the gas flow inlet of the flow passage and the by-pass, so that the counter-fire propagation can be prevented. In this case, the impact waves are not mitigated at all, and an excessive pressure condition exists inside the flow passage. Thus, there remains disadvantages in that damage is likely to be caused in places inside the flow passage.